Impedance-matching fluid amplifier



July 4, 1967 E. 1 SWARTZ IMPEDANcE-MATCHING FLUID AMPLIFIER Filed June l2, 1964 in the design of fluid systems United States Patent O 3,329,152 IMPEDANCE-MATCHING FLUID AMPLIFIER Elmer L. Swartz, Falls Church, Va., assigner to the United States of America as represented by the Secretary of the Army Filed June 12, 1964, Ser. No. 374,862 3 Claims. (Cl. IS7-81.5)

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the pay ment to me of any royalty thereon.

This invention relates to pure fluid amplifiers, and more particularly to impedance-matching in pure fluid amplifiers.

Fluids in fluid-jet amplifiers have three signicant properties: mass, viscosity, and compressibility. Aside from the basic energy fiux associated with the jets, significant manifestations of these properties include wave motion, energy dissipation, and gross turbulence. These phenomena are partially beneficial, and yet also introduce inherent limitations to the operation of the fluid amplifiers.

Wave motion in fluid-jet amplifiers is a factor frequently causing unsatisfactory operation. Its mechanism is not well understood, but the seriousness of the dynamic instabilities which result are clearly discernable. Most of these effects can be traced to the interaction of the amplifier with its inputs (source impedance-matching) or with its outputs (load impedance-matching).

In the design of fiuid amplifier systems (for example, fiuid amplifier systems to perform logic operation), it is desirable that each amplifier or element in the system be one standard size. Actually, one of the existing problems is in feeding the output of a first device to the controls of a second device when the physical construction of the second device limits the tiow below a certain value. Since the output dimensions of a given unit` are generally larger than the controls, it becomes impossible (using conventional units) to operate one into the other where the two units are identical. Actually the second (driven device) must be several times larger as a minimum. Without a dump, or bleed, the system becomes filled with fluid and ceases to operate.

Another problem is the loading effects in sensitive circuits, for example, a change in the load can be reflected into the interaction chamber of a fluid oscillator causing a change in frequency.

One successful scheme employed to isolate the load from the interaction chamber, and thereby prevent load impedance mismatching, is described in the copending application of Romald Bowles, entitled Pressure Recovery from Bistable Element, Ser. No. 288,567, filed June 17, 1963, now Pat. No. 3,267,947, and assigned to the same assignee as the present invention. The Bowles disclosure involves the placing of ducts extending from the output passages of the fluid amplifier downstream of the region of interaction between the control and power stream, with these ducts communicating with a predetermined fluid environment. As disclosed in the Bowles application, these ducts are in the pla-ce of the fluid amplifier. They have proven highly satisfactory in isolating the interaction chamber and the load in fluid amplifiers, eliminating many of the aforementioned difficulties associated with impedance mismatching. As pointed out in the Bowles application in order to achieve good self-adaptive regulation of the units it is necessary that the bleed ducts be substantially without discontinuity. With some systems, and some fluid elements, this requirement places a severe limitation upon the compactness and/or geometry of the unitor system.

An object of this invention is to provide a self-adaptive, impedance-matching fluid amplifier which is simple to con- ICC struct and may be used rwith fiuid elements and systems without problems.

Another object of this invention is to provide an irnpedance-matching element in the form of a bleed which can provide a short, unobstructed path between the center of the power stream and a predetermined fluid sink.

These and other objects of the invention are achieved through applicants discovery that bleedl ducts can efiectively be provided in a plane perpendicular to the plane of the amplifier.

The specific nature of the invention, as well as other objects, aspects, uses and advantages thereof, will clearly appear from the following description `and from the accompanying drawing, in which:

FIG. 1 shows a self-adaptive fluid amplifier employing orthogonal plane bleeds in accordance with the teachings of this invention.

FIG. 2 is a side elevation of the amplifier shown in FIG. 1.

FIG. 3 shows an alternate embodiment of this invention using a single orthogonal plane bleed duct.

Referring now to FIG. l there is shown a bistable fiuid element provided lwith a self-adapting orthogonal impedance-matching bleed constructed in accordance with the teachings of this invention. The fluid amplifier 10 consists essentially of a power jet nozzle 11, control nozzles 12 and 13, an interaction chamber 14, and output channels 15 and 16.

A common method of construction of fiuid amplifier devices, known in the art, is a laminate type of construction. The nozzles such as 11, 12, and 13, and the channels 15 and 16 are etched or machined out of a lower block of material 17 such as brass, plastic, or glass and are sealed with a cover plate 18. In the embodiment shown, cover plate 18 is illustrated as clear plastic for convenience but may be of any suitable material compatible with the fluid used. The base 17 and cover plate 18 may be secured together either by cementing or with machine screws, or any of a number of similar methods known in the art. Of course, channels may be partially formed in each half of the mating plates 17 and lSl; however, this presents an additional problem of critical registration of the plates and is not normally preferred.

Although there are some specialized exceptions, fluid amplifiers are in the main two devices. That is, in reference to FIG. la, fiuid issuing from nozzle 11 is a power jet stream and the information content of this power jet stream is derived from the position of the stream--issuing from channel 15 or 16-in the plane of the paper. It is this plane in which the bleeds of the prior art, of which applicant is aware, are placed. This plane, the plane in which the fluid power jet stream is moved, switched, or altered in order to produce an information signal output, will be defined for the purposes of this application as the plane of the amplifier.

Applicant has discovered that bleeds to self-adaptively match the amplifier to its load may be effectively placed with their longitudinal axes out of the plane of the amplifier. The embodiment of FIG. l shows this principle applied to a bistable fluid amplifier, with the bleeds shown at 21 and 22. As will be appreciated by those skilled in the art, in `such an amplifier a fiuid jet stream issuing from nozzle 11 will become attached to the wall 14a or 14h-either position being a stable position of the amplitier. Attached to the wall 14a, for example, fluid will issue from channel 16 and will continue to issue from channel 16 until a signal is applied at control nozzle 13. A signal at control nozzle 13 will switch the power jet to the channel 15 where it will remain untill a subsequent input at nozzle 12.

In FIG. l the lid 19 represents a load lon the fiuid amplifier. It will be understood by skilled persons that load 19 could be any of a number of things such as a moving piston or another fluid amplifier. The fluid power jet issuing from channel 16 will encounter the discontinuity represented by load 19. In the absence of bleeds 21 and 22 the effect of the load upon the operation of the liuid element would depend both upon the type of fiuid element and the magnitude of the impedance mismatch. In the extreme, fluid reflected from a load 19 can cause a bistable amplifier such as 10 to switch in the same manner as if a control signal had been applied at 13. Even a slight load mismatch in a fluid oscillator will cause a very pronounced shift in the oscillator frequency. These effects are minimized or completely eliminated through the use of applicants orthogonal plane bleeds 21 and 22. These bleeds 21 and 22 prevent the iiuid disturbances created by the load 19 from being reflected back into the interaction chamber 14 and affecting the operation of the device, and yet do not disturb its normal (no load) operation.

As shown more clearly in FIG. 1b the bleed 22, which is identical to bleed 21, is comprised of two openings 23 in the covers 17 and 18 of the amplifier, above and below the amplifier channel. The openings 23 communicate with a substantially straight, unobstructed, diverging channel 24, with a longitudinal axis 27. The bleeds lead to a predetermined ambient fluid condition or external liuid sink. As is evident from an inspection of FIG. 1b identical bleeds 22 are provided on either side of the channel in both cover plates 17 and 18. This is the preferred construction. However, as shown in FIG. 2, which is a side view similar to .that shown in FIG. 1b, and using the same reference numerals, a bleed channel on only one side of a channel and in a single cover is yall that is required. The advantage to this construction is, where the fluid amplifier -channels are all formed in one cover,

providing the bleed duct in this cover eliminates any problems of registration of the covers.

The location of the bleeds 21 and 22 has an important bearing on their effective operation. In general, they should be located in a relatively high pressure region of the power jet, yet down stream (away) from the power jet nozzle. Several power jet nozzle widths down streaml from the apex of the splitter gives a preferred location for most units. Additionally, it is desirable .that the output channel in which the unit is placed is unobstructed between the load and the bleed. Further, in the preferred embodiment, the opening 23 of the bleed extends substantially the whole width of the channel in which it is placed.

Applicant has also found that if the bleeds are placed where there is a sudden expansion of the power jet stream, improved results are obtained over those obtained with straight channels. The preferred embodiment of this invention, shown in FIG. 1, shows the bleeds so placed.

Many modifications will occur to persons skilled in the art, for example, rectangular slots and channels can be used, although they are harder to manufacturer than the round channels shown. Also, in some cases it may be desirable to make the openings 23 larger than the output channels, which would have the effect of having the bleed channel able to absorb vthe entire power jet stream.

It will be apparent that the embodiments yshown are only exemplary and that various modifications can be made in construction and arrangement `within .the scope of the invention as `defined in the appended claims.

I claim as my invention:

1. A fluid amplifier comprising: a iiuid powered jet nozzle, control nozzles adjacent said jet nozzle and sidewalls continuously extending from said control nozzles; a splitter between Said sidewalls forming between said sidewalls and said splitter a pair of output channels; an interaction chamber formed between said jet nozzle, said control nozzles, said sidewalls and lsaid splitter; said jet nozzle, said -control nozzles, said sidewalls, said splitter, said interaction chamber and said output channels being in a single plane; a bleed -channel communicating with a low pressure 'sink Iand located in each of said output channels downstream of said interaction chamber and extending out of and perpendicular to said single plane, said bleed channels extending above and below said single lane. p 2. A device according to claim 1 wherein said plural bleed channels in each output channel are in axial alignment.

3. A fluid amplifier having: two layers of laminar material; a fluid powered jet nozzle, control nozzles Iadjacent said jet nozzle, sidewalls continuously extending from said control nozzles; a splitter between said sidewalls forming between said sidewalls a pair of output channels; an interaction chamber formed between said jet nozzles, said control nozzles, said lsidewalls and said splitter; said interaction chamber, said splitter, said jet nozzle, said control nozzles, and said sidewalls being in the same plane as one of said layers; a pair of bleed passages in ea-ch of said layers of laminar material Iand communieating with said output channels downstream of said interaction chamber; each of said pair of bleed passages being in yaxial alignment and being perpendicular to said same plane; each bleed passage comprising a port in the output channel and leading to a diverging discharge channel in said respective layer of laminar material.

References Cited UNITED STATES PATENTS 3,174,497 3/1965 Sowers 137-81.5 3,181,546 5/1965 Boothe 137-81.5 3,207,168 9/1965 Warren 137-815 3,209,774 10/1965 Manion 137-815 3,225,780 12/1965 Warren et al. 137-815 3,240,219 3/1966 Dexter et al. 137-815 3,244,370 4/1966 Colston 137-815 X 3,261,372 7/1966 Burton 137-815 3,267,947 8/1966 Bowles 137-815 3,270,758 9/1966 Bauer 137-815 M. CARY NELSON, Primary Examiner.

S. SCOTT, Assistant Examiner. 

1. A FLUID AMPLIFIER COMPRISING: A FLUID POWERED JET NOZZLE, CONTROL NOZZLES ADJACENT SAID JET NOZZLE AND SIDEWALLS CONTINUOUSLY EXTENDING FROM SAID CONTROL NOZZLES; A SPLITTER BETWEEN SAID SIDEWALLS FORMING BETWEEN SAID SIDEWALLS AND SAID SPLITTER A PAIR OF OUTPUT CHANNELS; AN INTERACTION CHAMBER FORMED BETWEEN SAID JET NOZZLE, SAID CONTROL NOZZLES, SAID SIDEWALLS AND SAID SPLITTER; SAID JET NOZZLE, SAID CONTROL NOZZLES, SAID SIDEWALLS, SAID SPLITTER, SAID INTERACTION CHAMBER AND SAID OUTPUT CHANNELS BEING IN A SINGLE PLANE; A BLEED CHANNEL COMMUNICATING WITH A LOW PRESSURE SINK AND LOCATED IN EACH OF SAID OUTPUT CHANNELS DOWNSTREAM OF SAID INTERACTION CHAMBER AND EXTENDING OUT OF AND PERPENDICULAR TO SAID SINGLE PLANE, SAID BLEED CHANNELS EXTENDING ABOVE AND BELOW SAID SINGLE PLANE. 